Explosively actuated tools



July 19, 1960 R. .1. KoPF ETA@ ExPLosIvELY ACTUATED TooLs x-il'd nay 14, 1953 6 Sheets-Sheet 1 July 19, 1960 R. J. QPF my 2,945,236

ExPLosIvELY -Ac'rU'rEn Toons `e sheets-sheet 2 Filed May 14, 1953 f/S M6. m e ai d R Vd HN A m www MM Mmwo 3M w n w -w Q f7 K -Mm :1:1

July 19, 1.960

R. J. KoPF r-:TAL ExPLo'sIvELY AcTuA'rEn Toons 6 Sheets-Sheet 3 Filed May 1 4, 1953- of mm. Mm rv J E NKHr [.ed WJHM um fmw. m mfg@ www J wy RB M,

July 19, 1960 R. J. KOPF ETL ExPLosIvELY ACTUATED Toons 6 Sheets-*Sheet 5 Filed May 14, 1953 s M ons 4N mnr .ea R JHM m /dwf Mr M LA www fm July 19, 1960 R. .1. KOPF ETAL 2,945,236

ExPLosIvELY ACTUATED TooLS Filed May 14, 195:5 6 sheets-sheet e A'T'OR/VEYS United States Patent@ l" j 239452136 r 1'i`ini1.o'sufrir;A-crnzsrrn;Tours;Y iiwinnd-ai Knpennaznnbert w: Henning, Rnnkyzniver, and RogerMrsln'Hudson, Ohio, assignors5 byym'esne assignmentsgrtalin Mathieson Chemical Giol'ptlfaiiqlln incorporatiomofsVllfginiteV Filed'May 1'4519153; Ser. No. 3555934' ,Thisf invention relates toU improvements in, a fastener drivingtool and-moreparticularlv to a-vtooloft-lenpowder actuated-type: l The object off the present invent-ioniisftoprovi'defa powder-actuated fastener driving A-tool characterized by its structural simplicity,- the economy4- ofi its.'manr-ifacture,` easef-offassemhly ofiitsvparts; itsoperatingeizieney, its many safety features; itsease ofv operation, audits-universal" construction forl use` under manydifferentconditions'. v`

Other features ofl this invention reside inv the arrangementl and design ofthe-parts for',carryingnoubtlieirv aplziropriatev functions. Other objects and'A advantagesn of Vinvention wil1=be apparent from the accompanying drawings gand descriptionandr the essential features will-be setffortlr in the appended claims.

In the drawings;

Fig. l is a vertical, longitudinal; sectionaln view of the'powder actuated tool in the safety' or normal position;

Eig. -2is aside elevational view ofthe toolilrFi'g.v 1 partly iny vertical, longitudinal section, with the` barrel muzzle andtool. pressed against the workpiece on the left with the tool' in the readyfto-,re ygionsition;I

Fig: 3 is a vertical, transverse sectional view, taken along'the line 3`3 in Fig, 1 through the ringipimpayvl, and .trigger of the powder charge iii-inKgniezrns;`

Fig. 4 is a vertical, transverse. sectional viQW, taken alongthe line 4-4` of Fig. 1 through the breechvblock and' front ofthe trigger guardi Fig. 5' is a vertical, transverse sectional View taken along' the line 5-5 of Fig. l through thescreyv, coupling between the breech blocky and barrel whenthe; tool is fully locked;

- Fig. 6- is a vertical, transverse sectional view taken alongthiej line 6 -6 of Fig. 1 through the rear, of the extension rod, unitA with a portion of, the housing; sur,-

ronndingthe, barrel. broken away to expose an interlock pin;

Fig. isf ai longitudinal,t radielly` extending?, sectional vView taken,l alongthe line 7-. 7v of Figi 6 through-the interlock pin and, barrel guide, screw;

Eig. 8s is a vertical, transverse sectional view.- taken action of the interlockpin;

Figs. 9 and, 10 are. side elevationali viewS; O f thel tool respectively with its assemblies screwcdf together for Iiringand pivoted. open for loading;

Fig. 1 1- is a. vertical, transverse sectional vien/taken along the line 1-1 L114 in Fig. lithroughttfhe spring loaded extension rod release buttonand the, detiector-pad, ash shield telescopic mounting in; the tooly tllciilsing;v

' Eig 12is. a., verti; al,I transverse .sectional view taken along the line 12-1'2 in Fig. 1 looking @weather-nain Shield;

Eig. 1335-21 sectional viewV takcnalongfthsfln-1341i?, erlig.. 6 of, the, barrel .guide slot finit-hc utside. .surface fbarrel with the. barrel guide 'Screw Iinsection 4,eo-

V acting therewith;

along the line, 8.- 8 of Fig.` 7V to. disclose; the -locking 2.. Fig. 1,4 :is aside ehn/atiollllf vrpof-i @M991 @il-L: unsuccesstulfattemrt-has:been medew-fir barret axis was tilted, a- Substantial l2111101.11wstiiires to the normal to the workpiece surface; v Ivligg 15 isa; side elevationalview,partiallyvin"section, of, the l10011 in.v a ready-tofu@ psiticn; con Sr to Fig.; z but:y having-af barrel extension; an@ titr @me rod use; A f

AFiegltiis a.lo11git\1 c1 ira1,y verticalSeiipnfvienthrorgh an modiedf form O ffdetaclieb'l Direct' at@ the toot breech, with: this View;l eensrallr Corresponding; to; the hreechfportionofliig. 1;

Fig.,- 172 iS- a1 vertical transverses Sectional-,f vien` tahiti along Lthe line 1711.7 O ff; Ein- 1.65 andi genera yn correa spending to Fig. 8;

Fig- IS-vis; aivertials'-lonsitudinal Section--tial enlthrougii ,011.;- rod; ansi i its; springe biased release. betten correspondi g t portion; onggthe,l left offFig.- lvbutfwith the extension: d E

ICC

u can... Maven tt,

Eig.v 1,9isj a, critical,v transverse, sect-ionalfview. take along] the line 19T-1,9, of Fig: v181kr and` generally. corren Spendingte h-1Qwer haliefeEig.- 11;.

Bcforefthe -toQlherellnstrated isspecicnlly described; it is to be understood that the invention here involved' is; not lingiiteiito thfeistructural;'detailsor. arrangements of par-ts here; shownsinee toolsembodying ,Y thepre'sent in ventionmay;l talgevarious forms. It-also isto vbe under.- stood` t- I the phrascology orterminology herein ein ployed forgpurposesfofdescription and'. not offlimitation sincetheA s cope.` of the present inventionis denotedv bythe appended claims.

Those familiar with this art will' recognize that the presentinventionmayi be appliedJ in manyways, butfit hasbeen; chosen to illustrate the. same asa'- powder activi'- atedg'fastener driving tool; Many. of thefeat-ures may be u sedf, on: othertools, otherI powder.v charge Vactuated devices,- and othergprojectileJor fastenerfiring ordriving devices.. The tool is illustrated'` in generalin- Fig It-A comprises-V interconnected` pistolf grip. or handle`- 2Q, barrel lzglandgagpowder charge tiring means 28: The toolj cgi; be divided' into two m-ajonpaits, thebarrel assembly and; thebreech assemblyn19, showny Fig. -1 generally on the left and* right off section` line 5--5` respectively and in; Fig. 1 0 on` the left and right respectively. The barrel assembly'l has a barrel'ZZ with a'` charnher in its breechfor receiving a fastener unitconnprising infig. 2a, cartridge case'2'3a with a priiner` and powdercharg and:` a fastener 23b sov that the fastenerl will be driven throughy the barrel boreV when the primer isfstrupk' t explode. the power charge. The breech assembly n19 has a powdercharge-y firing means, generally shownft 28 in Fig. 1 andK including a firing pin for striking said primer and= a trigger Vfor release of the firing pin.W tooll has ahousing 21' ysurrounding the-barrel?, and the firing means 28 withl the barrel 22- mounted for tele.- scopic endwise or axialvmovementl in and relative` to the housing betweenl a normal, muzzle advanced, safety, `first position in LEig. 1' and a muzzle depressed, ready-tdire or vtiring, second position in Fig/2. The tooljis moved endwise between' the lirst and second positions by pressing the barrelnnuzzle against theworkpiecg 2S von the left in Eig 2 into which the fastener 23h is t9 ibe driven and then. -telescopically'moving theltoonli housing overthe -barrel =It7should bencted thatthebarrl breech and the tiring means -28 'in .the first andsecond positions VareV respectivelyspaced Widely apartandfadjacent each other `while the `housing'Zl moves endwise in: travelingrel tive to, the barrel from the rstf vto .the second position es :be brought Outfinffilrtlidsta hereinafter, this endwise movement of the tool housing 21 relative to the barrel from the iirst to the second position cocks the iiring pin for release by the trigger in the tiring means 28.

The muzzle of the tool also includes a ash shield 24 in Fig. 1 biased toward the left by spring 26 so as to rmly engage the workpiece 2S in Fig. 2 to protectthe tool operator from ricochets and spalling of the Workpiece 25.

The barrel assembly 18 in Fig. l has barrel 22 surrounded by a rst portion of the tool housing 21 hereinafter called barrel housing 50. The breech member or assembly 19 has the powder charge iiringmeans 28 surrounded by the second portion of the housing 21 hereinafter called breech housing 27. This latterl housing portion comprises a one-piece receiver housing 20a, hand grip 20 and trigger guard 20b and also includes a firing mechanism lhousing 30 inserted into the cylindrical bore of the receiver housing 20a and held therein by a screw l31. Y A tiring pin 34 in Fig. l travels in the bore of the firing mechanism housing 30 and is resiliently biased by a tiring pin spring 35 to move toward the left in Fig. 1 toward the barrel in the general axial direction of the b arrel bore. The tiring pin spring 35 is captured between tv he tiring pin bore and in the `firing mechanism housing 3.0 and an aligned bore in the receiver housing 20a so that the firing pin is normally urged to the left in Fig. l until it encounters the shoulder 30a of its surrounding bore.

A breech block 37 in Figs. l and 4 is mounted for relative axial movement but no rotational movement relative to its surrounding housing 27 in the bore extending inwardly from the left into tiring mechanism housing 30. A breech block screw 39 has its head traveling in an axially extending slot 3017 of the firing mechanism housing 30 so that relative axial movement but no rotational movement can take place. The housing 30 is movable axially relative to not only the barrel 22 but also the breech block 37 between the normal, iirst or safety position (Fig. l) and a ready-to-re position (Fig. 2), in the latter position the breech block 37 being located closer to the rear of the housing 27. A firing mechanism spring 38 biases the breech block 37 toward the left in Fig. l so that the breech block will always be normally in the safety position advanced toward the left for detachable connection over the chamber of the barrel. Both springs 26 and 38 normally urge the barrel and the breech block 37 toward the left in Fig. 1 so as to normally assume the safety position. However, when the barrel muzzle is pressed against the workpiece 25 in Fig. 2, the force of these springs is overcome so that a firing pin pawl 42 on the firing pin 34 moves into contact with a cocking rod 40 on the breech block for exerting a force against the pawl in the direction of tiring pin cocking travel as the tool moves from the rst to the second positions respectively shown in Figs. l and 2 so as to cock the iring pin. It should be noted that the tiring pin 34 is cocked in response to the relative movement between barrel 22 and the tool housing 21 from the iirst to the second position since the cocking pin 40 is iixed with respect to the barrel. The cocking of the tiring pin is entirely independent of actuation of trigger 46 pivotally mounted by a trigger pivot pin 47 in a slot 30e cut in the bottom of the firing mechanism housing 30 in Figs. l and 3. The Ytrigger 46 is not only inoperative to cock the tiring pin 34 but also normally inoperative to release the iiring pin when the tool is in the Fig. l position.

However, the trigger 46 is manually operable to release the firing pin 34 to strike the primer and explodethe powder in the cartridge case 23a when the tool is in the ready-to-re position of Fig. 2. As the trigger is pulled and pivots countercloekwise around the pin 47, a sear 46a on said trigger moves upwardly to depress 4the iiring pin pawl 42 in a direction at a right angle with respect to the tiring pin travel and against the resilient bias of its tiring pin vpawl spring 43 so that the tiring pin moves' free of the restraining action of cocking rod 40. Then, the tiring pin spring 35 will drive the firing pin 34 toward the left through the aligned tiring pin hole 37a to strike the primer of cartridge case 23a. l

It should be noted that the cocking rod 40, tiring pin pawl 42, ring pin 34 and' irirg pin hole 37a always keep in correct alignment because the breech block 37 cannot rotate since its guide screw 39 travels onlylongitudinally in slot 3011 of the tiring mechanism housing30 and since cocking rod 40, the trigger 46 and the firing pin pawl 42 all travel within the restraining side walls of slot 30o of the ring mechanism housing 30, as seen in Figs. 1, 2 and 3, to prevent rotation of these parts relative to housing 30.

After the trigger 46 has been released, the trigger return spring 49, bearing against the rear edge of the trigger rotates it clockwise to the Fig. l position, so that the pawl 42 can be pushed without interference to a position above it, corresponding to Fig. 2, when the tool is used again. The trigger spring 49 is of T-shape with an upper cross bar thereon vertically inserted up into a pair of slots straddling the slots 30C in the bottom of the firing mechanism housing in dotted lines in Fig. 3.

Although springs 26 and 38 normally urge barrel 22 to the Fig. 1 safety position, tiring pin spring 35 also urges it toward the left and a safe position through interconnected pawl 42 and rod 40 to assure that iiring pin 34 will be safely spaced from cartridge case 23a.

Although the -breech assembly 19 includes an interconnected breech block 37, tiring pin 34, trigger 46 and handle or pistol grip 20 extending laterally from the bore axis of the barrel member, the parts are specifically constructed for rapid and convenient assembly. 'It breaks down into two units. A rst unit comprising the integrally formed receiver housing 20a, hand grip 20 and trigger guard Zb having an opening in the receiver housing from the front thereof (from the left in Fig. 1). The front of the trigger guard, instead of being solid as a conventional trigger guard, is divided into two arms by a downwardly protruding slot 20c in Figs. l and 4 having an open front and an open top communicating with the cylindrical bore in the front of the integral member for surrounding the firing mechanism housing 30. The second unit comprises a firing mechanism with the tiring mechanism housing 30, tiring pin 34, tiring pin spring 35, breech block 37, firing mechanism spring 38, breech block screw 39, cocking rod 4G, tiring pin pawl 42, ring pin pawl spring 43, trigger 46, trigger pivot pin 47, and trigger return spring 49. This second unit, including the aforesaid respective parts, is telescoped rearwardly during assembly into the 'cylindrical bore in the front of the receiver housing 20a. Since the downwardly extending trigger 46 and trigger return spring 49 are less in width (Fig. 4) than the slot 29C in the front of the trigger guard, this second unit can be telescoped rearwardly as a unit and then can be secured in position by the screw 31. It should be noted that the tiring pin spring 35 is housed in aligned bores in the receiver housing 20a and tiring mechanism housing 30. This two unit construction permits the entire second unit to be assembled within the `firing mechanism housing 30 before assembly into the receiver housing 20a since the trigger and its return spring are narrow enough to pass through the slot 20c during assembly.

The barrel assembly 18 includes the barrel 22 surrounded by barrel housing 50, as mentioned before. A screw 53 secures an outer tube collar 51, telescopically lmounted over the barrel, within an outer tube 54 and also secures a` hinge bracket 52 to the outer surface of the outer tube 54. The barrel housing 50 comprises collar 51 and tube 54.

The chamber Iof the barrel 22, located at the breech, has a detachable breech plug 56 insertable into or removable irom saidchamber during loading and unloading With the bore of said plug adapted to receive a cartridge l? ,barrel chamber and telescopes it over either rod 61a or 4rod 65 in Fig. 10 to eject the spent cartridgecase 23a. Then, astener-23b (Fig. 2) isinsertedpoint first into the barrel bore through the breech and a new cartridge case 23a is inserted into the bore of the breech plug S6 after which the breech plug is inserted into the barrel chamber. The tool is locked or closed by grasping the outer surface of the barrel assembly 18 in one hand and the hand grip 20 in the other and then reversing the opening or unlocking procedure in swinging, telescoping and rotating through a one-eighth turn the breech assembly 19.

As mentioned before, `after the tool assemblies are locked closed in the Fig. l position, the tool housing 21 must be telescoped to the left `over the barrel 22 to cock the ring pin by moving the tool from the first, normal or safety position in Fig. 1 to the readyto-ire or second position in Fig. 2. Although during this movement the tube collar 51 must telescope over the barrel 22 in Fig. l, there must be very little relative rotation therebetween or else the screw threads 22t and 37t on the barrel breech and the breech block 37 respectively may unscrew and dangerously open the breech `during firing. The screw S3 in Figs. 1 and 13 is used not onlyto assemble the parts but also `as a barrel guide screw by coacting with the slots 22a, 22b. Hence, the outer tube collar 51 can be moved endwise or axially in a telescopic manner over barrel 22 but will not appreciably rotate relative thereto. The slot has a widened portion 22b for cooperation with the barrel guide screw 53 when the tool approaches and is in the ready-to-fire position of Fig. 2 so as to prevent turn jamming the barrel in the ready-to-re position. The end 22a of the slot is of minimum width to guide the barrel guide screw 53 so as to minimize rotation of the barrel 22 relative to its surrounding barrel housing 50. If this narrow width were carried the full length of the slot or groove, necessary minimum rotation of the other parts of the Vtool required for clearance and ease of operation might permit the tool operator, bytwisting the tool component parts relative to each other after the tool was depressed against the workpiece in the Fig. 2 position, to bind the side of groove or slot 22a against the barrel guide screw 53 by turn jamming to Vjam the barrel in the Fig.` 2 position for so called air firing. Then, the tool could be removed from the workpiece, while keeping the tool parts bound in the Fig. 2 position, so as to lire the fastener like a gun driven projectile into the air by air firing instead of into the workpiece. lf turn jamming could occur, the tool could be tired in the same manner as a gun with fastener 23b being dangerously used as a projectile. This tiring could occur even though the barrel muzzle was not pushed up against a workpiece 25 since any turn jamming would prevent the barrel 22 traveling forwardly to its Fig. l safety po sition under the =bias of springs 26 Iand 38 upon removal of the tool from the workpiece. The groove end 22h is thus widened so that once the tool is locked and brought to the ready-to-re position in Fig. 2; the ybarrel guide screw S3 is in the wide portion of the guide groove to prevent turn jamming.

After the one-eighth turn lockingaction has taken place so that the tool is locked in the Figs. l and Sposition, and the housing 21 is moving to the left `over the barrel 22 from the Fig. l safety to the Fig. 2 ready-to-i'ire position, an interlock means on the housing 21 is responsive to the movement of the housing 21 relative to the barrel approaching said ready-to-fire position for locking the breech block 37 and the whole Ibreech assembly 19 against detachment from the barrel 22 and barrel assembly 18 during firing. 'Figs 6, 7 and 8 disclose an -interlock pin 66 of generally L-shape having its short legs traveling above a flat 22C on the barrel while the remainder of the pin slides in a through radial slotSlc in the outer tube collar 51 and a peripheral slotSld p 8 also therein with both of these slots generally extending in and interlock pin 66 movable in the barrel axis direction. Fig. 7 discloses the interlock pin 66 inV the .unlocked position in solid lines when the tool is inthe Fig. 1 position and `discloses the interlock pin in locked position in dot-dash lines when the tool is in the ready-to-re Fig. 2 position since the shoulder at the left end of iat 22C pushes against the vertical leg of the interlock pin 66 to move it to the dot-dash line position. In the dot-dash line or locked position, the horizontal leg of the interlock pin 66 travels axially to the right in Fig. 7 back into the cutout formed by the `bore in the filing mech- ;anism housing 30 past the overlatch pin 63 so that the assemblies cannot become fully unscrewed. Any attempt `to rotate the rng mechanism housing 30 relative to the outer tube collar 51 for unscrewing the threads 22t on the breech of the :barrel would be prevented because the overlatch pin 63 in Fig. 8 cannot rotate outof the peripheral groove 51b into the clearance at 51a for removal since the interlock pin 66 blocks its travel.

It should also be noted that if the assemblies are not fully screwed together when the breech assembly 19 has been turned relative to the barrel assembly 18, movement of the tool from the Fig. 1 toward the Fig. 2 position will be blocked for safety purposes when interlock pin 66 abuts against the shoulder in the bore formed by the overlatch pin 63 in Fig. 8 and thus prevent the tool from attaining the ready-toiire position of Fig. 2.

It should be also noted that interlock pin 66 is unlocked in response to the movement of the tool away from the Fig. 2 ready-toefire position since the shoulder on the right end of the barrel at 22C engages the vertical leg of the interlock pin 66 to pull it from the dotdash to the solid line position in Fig. 7. When the interlock pin 66 is in the dot-dash line position in Fig. 7,

.it is possible for the tool operator, Aby relatively twisting the tool assemblies 18 and 19 toward their unlocked position, to bind the lock pin 66 in this position against the side of its mounting slot in collar 51.V However, the barrel 22 is free to move a substantial distance toward the Fig. 1 or safety position as soon as the barrel muzzle is removed from the workpiece even though the interlock pin 66 itself may be jammed, because the at 22C between its end shoulders is of substantial length to serve as a lost motion movement transmitting means between barrel and pin and because springs 26 and 38 will bias the barrel toward the safety position.

This structure prevents (1) firing the tool in the unlocked position, (2) inadvertent unlocking of the tool in its ready-to-fire position or firing position, and (3) any deliberate attempt to turn jam the tool for air firing.

The timing between the barrelV guide slot action and the interlock pin action is clearly shown in Fig. 7. The interlock pin 66 is effective (moved to its dot-dash line position in Fig. 7) when the barrel guide screw 53 reaches the wide portion 22h of the elongated barrel guide slot in Fig. 13V.

Flash shield'24 and its appurtenant parts are shown in more `detail at the left in Fig. l and in Fig. 12. This ash or ldeilector pad shield 24 is telescopically mounted over the barrel 22 near its muzzle and is adapted to engage for safety purposes the workpiece 25, as shown in Fig. 2, during `driving of the fastener 23h. This shield 24 has a plate 68 rotatably secured thereto by a screw 72 and nut 73 connection in the center of the plate 68 but laterally spaced from the bore of barrel 22. A hy- ,drogen braze secures the plate 68 to a shield tube 70 eX- tending away from the shield 24 toward the right in Fig. l. Both the shield 24 and the tube 70 are telescopically mounted over the barrel 22. The shield tube 70 telescopes through the open end on the left and into the outer tube 54 in Fig. 1.

The plate 68, screw and nut connection 72, 73, and the shield 24 coact together to form an adjustable gage 11 frombeingvused' in the absence of parts 24 and 26. YSince it is always desirable for safety reasons to use the safety ash shield 24 and its spring 26 so as to use the tool properly, means has been provided to prevent the firing of the tool unless they are used. This is a safety feature protecting the tool operator primarilyl against ricochets and incidentally against damage to his ear drums because this structure acts somewhat like a silencer, etc. This takes the form in the present disclosure of a barrel engageable latching means located between the stop ring or collar 51 in Figs. 1 and 7 land the right end of shield spring 26. A split annular gripper member 80 serves as a lock or latch adapted to engage in the groove 22e on the periphery of the barrel with an annular C- shape spring '81 biasing these members inwardly and tending to force the split gripper portions closed or into engagement with this groove 22e. In the latching position the location of these split gripper portions and groove is such that if they are permitted to ,engage the groove in the barrel, forward movement of the collar 51 relative to the barrel 22 is stopped after a predetermined point so that the collar 51y prevents further movement to the Vfiring pin cockingposition. The bore of the gripper portions on the left in Figs. ,1 and 7 is constructed in the form of a female cone with its large end to the left. A barrel lock release 82, annular in form, has a male cone surface on the right designed to mate 'and cooperate with the female cone previously described.

per portions 805 out of latching engagement with the barrel lgroove 22e so as to keep the barrel gripper portions 80 in the unlatching position during normal usage. However, when the shield 24 and spring 26 are removed, there is no spring pressure against barrel lock release 82. Therefore, the annular spring 81 resiliently pulls the gripper portions 80 inwardly into engagement with the barrel surface so that they willengage in the groove 22e as soon as the tool is moved suflciently toward the ready-to-iire position. Hence, the latching means would be in its latching position, being biased thereto by the spring 81, for preventingfiring of the tool if shield 24 and spring 26 are eliminated and the tool is not properly used.

When the fastenerZSb is to be driven into a depression on the surface ofthe workpiece, such as in workpiece 25 in Fig. l5, the barrel muzzle must during firing extend out beyond the ush relationship with the end of the flash shield 24 shown in Fig. 2. Since the tool, as illustrated in Fig. 2,V could not be used -for this type of job because the protruding barrel will not be moved back into the housing `far enough to cock the firing pin, a barrel extension S4 in Fig. 15 is 4generally used and has female and male Vthread portions onopposite ends for detachable connection between the muzzle ofthe barrel 22 and the thread protector barrel cap 75. Then, the firing pin and depressible pawl will be properly aligned with the trigger for firing when the tool parts are moved to the ready-to-fire position shown in Fig. 15, corresponding with Fig. V2. Y

A storage recess is provided in the pistol grip handle 20 of the tool for receiving when not in use the barrel extension 84 or any other type tool attachment desired. This storage recess or bore 20d in Fig. 1 is also provided with a locking means for `detachably locking the barrel extension 84 therein. This locking meansl comprises a one-piece, at resilient spring latch 89 frictionally and detachably secured ina recess 20e inthe pistol grip handle 20 extending inwardly .from the bottom of the pistol grip in the same manner and direction as the bore 20d. The latch has a mid-portion 89a, substantially flat, bearing against the bore side of the recess 20e, an attachment retainer portion 89h` on Aone end resiliently biased over the open lower endof the bore 20d but swingable away `a peripheral groove thereon. y v 4is located between the retainer 93 and bushing 96 so as rlease button movement. l bore portion spring loaded against the extension rod 95.

12 therefrom forremoval of the barrel extension, and its opposite end 89C bent back upon the mid-portion 89a with a sharp `dista-l end engaged in the recess side remote from the bore 20d. The distal end of portion 89b is rolled into a loop rotatably securing a r-ing 90 for manual manipulation of latch 89.

Within the handle bore 20d is also stored a disk adapter 86 for use in place of the thread protector cap V75 in either Figs. l or 15. This disk adapter has a sleeve 86a having internal sleeve-like cap 75 with a spring 87 with a generally annular portion resiliently engaged in a peripheral groove of sleeve 86a and adapted to resiliently hold a at, circular metallic disk pierceable by the fastener 23b as it emerges `from the barrel muzzle and before it enters the workpiece 25 or 25 so as to limit the penetration of the fastener 23h therein. j

As mentioned before, the surrounding housing 21 and tiring means `28 can be moved endwise relative .to barrel 22 in Fig. 1 by pressing the barrel muzzle against the workpiece 25 so that the tool will move from a normal, muzzle advanced, safety position in Fig..1 to a second, muzzle depressed ready-to-re `or tiring position in Fig. 2. However, springs 26 and 38 in Fig. 1 normally urge or 4bias the barrel 22 toward the first position `shown in Fig. 1. Comparison ofl Figs. 1 and 2 will also reveal .that lthe housing 21 and ring means 28 move relative to or advance toward the flash shield 24 when moving from the first position to the second position. Under some conditions, it is desirable to limit this approach vmovement so that they will never get together closer than a predetermined distance.

The structure for limiting or blocking the movement of the housing 21 relative to flash shield 24 includes the previously described brackets 77 and 52 in Fig. l with both having counter bores therein `for receiving the opposite ends of the tube 91. The bracket 77 on the left in Fig. 1 is xed to the outer tube 54 of the housingll Vwhile the hinge bracket 52 on the right is removably securedthereto for assembly by the barrel guide screw 53. A hollow extension rod is telescopically mounted Awithinthis tube 91. This rod 95 isformed from Seamless tubin-g, has a threaded outside surface and an axial through bore with the seamless tubing construction providing the bore without the necessity of deep-drilling.

VThe extension rod or screw 95 is counterbored from the right end -in Fig. l and a bushing 96 is inserted therein. 'This bushing 96 travels on a guide rod 92 anchoredpat its right end by a generally C-shape retainer snapped into A compression spring V94 Athreads in the release button and Vstraddles the extension vscrew rod 95, as more readily seen in Fig. r11. Vthan one-half of the circumference of this elongated Yhole is threaded while remaining portion (lower portion Less in Figs. 1 and ll) is relieved for clearance during re- 'Ihebutton 97 has its threaded When the bottom of the release button 97 in Figs. l and l1 is pushed upwardly by manually exerted pressure, the threaded portions will disengage to allow the extension rod 95 to move toward the left in Fig. 1 -under the pressure of spring 94. VWhen the release Abutton V97 is no longer depressed, the pressure of spring 98 moves .-1t downwardly in Figs. 1 and 11 to cause thread engagement 1av and to thus lock the extension rod 95 in whatever axial location it has assumed at that time.

A downwardly projecting stop shoulder 95a on the right end of extension rod 95 is adapted to engage an upwardly extending stop shoulder 77a on the supporting bracket 77 on the left in Fig. 1 when the extension rod 95 is fully extended to prevent theescape of the extension rod 95 during changing or indexing of flash shield 24 yif button 97 should be accidentally'depressed. A flat is milled on the bottom of the extension rod 95 in Fig. 11 since the threads on the lower side are never used. 'Ihe portion projecting above the flat provides the stop shoulder 95a and the top of the stop shoulder 77a coacts with the at to prevent rotation of the extension rod 95 so that the threads thereon are always facing upwardly `for the proper coaction withthe threads of the, release button 97.

f It should be noted that the barrel guide screw 53 in Fig. 1 is peculiarly located to provide a multiplicity of functions. It is threaded into the outer tube collar 51 to secure said collar to the outer tube 54 and the hinge bracket 52. The'rhinge -bracket 52 is .thus removable from the tools so that the extension rod tube-91 and the multiplicity of parts therein can be disassembled from the tool even though the lfront tube supporting bracket 77 is iixed to the outer tube 54. Also, the upper tip end of the screw 53 in Fig. 1 travels in the barrel guide slot 22a, 22b to prevent rotation of the barrel 22 relative to the housing while permitting telescopic movement therebetween. This structure provides easy assembly and servicingof the tool parts by authorized personnel.

When the tool is used in the manner shown in Figs. 1 and 2 and it is constructed without the barrel extension 84, the extension rod 95 and its associated parts are used as a safety locking means to prevent moving the tool housing relative to the barrel 22 to the ready-to-iire position in Fig. 2. The tool is normally manipulated by two hand operation necessitated by this safety locking means. One hand grips the pistol grip '20 with the finger in the trigger guard in front `of the trigger 46, as .on a conventional gun, while the other hand surrounds the outer housing of the barrel assembly with one finger, preferably the index finger, engaging the outer surface of the release button 97 to depress it into the outer housing. It should be noted that the outer housing, extension rod tube, and its supporting brackets are all encased within a rubber or plastic sleeve grip 99 except for the exposed release button 97, as seen in Figs. l, 2, 6, 9y and 11, for ease of operation and for appearance. -It can vreadily be seen that releasing or manually depressing the button 97 will make the safety operative or inoperative respectively to lock against or to permit axial movement of the extension rod 95. If the, button 97 is always depressed when the tool is being operated in two hand operations, the extension rod 95 will always extend forwardly toward the left in Fig. l into contact with the fiash shield. Then, since the button 97 is held in the safety inoperative or depressed position, the tool housing is permitted to travel the full distance toward the readyl to-fire or firing position in Fig. 2 in the normal manner.

`However, release of the button 97 will move the safety locking means to its operative position to prevent the tool from traveling further toward the ready-to-ire or firing `position if the tool parts are intermediate between the Figs. l and 2 positions at the time of button release. Then, the extension rod 95V will engage the back 0f the Viiash shield to space apart the housing and ring means 28 carried thereby from the ash shield 24 lso as to stop housing so that the pressing of the barrel muzzle against `the workpiece 25 cannot move the tool to the ready-tovfire or firing position in Fig. 2. This construction makes Of course, the tool can be red by one hand operation or without continuously depressing button 97 Then, vextension rod 95 is kept retracted within tube 9&1, as shown by the solid line position in Fig. l, and only the hand on grip 20 and trigger 46 is required. However, the safety can be made operative by depressing button 97.

When the tool is used with the barrel extension 84 in Fig. 15, the extension rod 95 is used for a different purpose. Here, the rod 95 assures that both the barrel muzzle and iiash shield 24 will be firmly against the workpiece 25 when the fastener 23b is driven and also permits angle iire control, the latter to be `discussed in more detail hereinafter. However, the operator must set rod 95 in a predetermined position dependent upon the work- "the relative approach movement of the flash shield and U piece depression depth. The operator depresses the release button 97 and pushes the barrel muzzle and flash shield 24 against the workpiece 25 with the barrel axis extending generally perpendicular to the fastener receiv-` ing surface of the workpiece. Then, the tool operator releases button 97 and never touches it againas long as the same size workpieces 25 are having fasteners driven therein, in other words, workpieces having Vthe same depression depth. Now, when the tool is used, the ash shield 24 will always be depressed firmly against the workpiece and angle fire control can be utilized so that the tool can only be fired if it is properly oriented with the workpiece.

Although the tool has basically the same angle re control with or without barrel extension 84, angle re control can be most clearly explained by referring first to Figs. 1, 2, 9V and 14 wherein the tool is used without the barrel extension 84. A comparison of Figs. 2 and 14 will reveal that merely making contact of the flash shield 24 and barrel muzzle with the workpiece surface is not sufcient to move the tool to the ready-to-iire or firing position since housing tube 54 and shield 24 act as stop means in Fig. 14 to prematurely arrest the movement. The vbore of barrel 22 must be approximately perpendicular to the surface of workpiece .25 in order to move thering pin pawl V42 into alignment with the trigger sear 46a. Squeezing the trigger 46 in Fig. 14 will never re the tool since both springs 35 and 38 bias barrel 22 and housing away from the ready-to-re or firing position while pushing the barrel muzzle against the workpiece (spring26 yonly pushes flash shield 24 against the workpiece but does not urge the barrel because flashshield 24 does not engage the barrel cap 75). Hence, the barrel bore axis cannot be tilted substantially from the normal to the workpiece surface if -iiring is desired, the maximum `permissible tilt here to have so called approximately perpendicular alignment is about 12 or less when the shield is inthe Fig. 12 position. The tool is capable of driving a fastener when the tool orientation is 12 or less but is incapable of driving 'when the tilt is over 12. Therefore, a fastener v23b cannot be driven at a dangerout ricochet angle against the Isurface of the workpiece ,especially when the flash shield 24 is raised from the workpiece surface, `as in Fig. 14, so as to permit the escape in a dangerous manner of either the ricochet, spalling, or -splattering of the workpiece material. Also, if the firing pin 34 is released after the trigger is pulled, the tool operator can be sure that the ring pin tip has traveled suiciently far to the left in Fig. 2 toV strike the primer of cartridge case 23a. A failure to iire therefore can be blamed only on a dud cartridge case.

It should be noted that the back of firing pin 34 has an extension rod 34a formed integral therewith and slidably in an aperture in the back of .the receiver housing 20u. The top or distal end of this rod extension34a in Fig. 2 is painted a contrasting color so that it is easily visible when it emerges at the mouth of the hole in the housing in response to the relative movement of the ring pin and barrel to the ready-to-iire position of Fig. 2 to serve as a combination tilt and ready-to-flre position indicator since it is not visible when the tool is in the safety position of Fig. l orV when it is tilted excessively, asi'n Fig. 14. When; thetool is correctly aligned and is inthe' ready-toLiire' position, the tip of the rod 34a is approximately ii'ushV with the housing outer surface, as shown in Fig. 2. This construction enables the operator todetermine-before' pressing the trigger that the tool is in its ready-tol-fire' position, to prevent dud shots with the tool out' of position, and to require holding the tool 'generally' square with the surface of the workpiece 25.

When' the barrel extension 84- is used, the angle fireV controlir takes place in substantially the same manner ex'c'ept that the extended rod 95 in Fig. 15, after being set in the`V aforcdescribed predetermined position correspondingV to"V the depression depth in workpiece 25', acts as a stop means (instead of the stop means formed by the left end of the barrel housing' 50- in Figs. 2` and 14) for engagement with the; back of the hash shield 24. Hence; this stopmeansrod' 95, hash' shield 24 and barrel muzzle inW Fig. 15 must beso-located that when the fiash shield 24 and the stop'rod 95: are engaged andwhen the ash shield 24? and barrel muzzle are pressedv against and into' engagement withJ the workpiece, the barrel bore must he'approximatelyperpendicular to the workpiece fastener receiving surface in order to move the firing pin 34 into the ready-tothel position inFig. 15 with the trigger scar 46a" and firing pinvpawl 42 aligned'. The adjustability of extension rod 95 assures that the left end of the rod 95 in Fig. l will be located at any predetermined distance aheadv of th'e housing 50 for determining the stopping pointof the shield 2'4' to correspond 'with the depth of the depression in the workpiece 25'. Hence, the extensionl rod 9S, when properly positioned will'assure that Both thejlarrel muzzle and hash shield 24 are properly against the workpiece before the tool can be fired'. The Barrel will be approximately perpendicular to the workpiece surface, the left face of shield 24 4in Fig. V15 will be approximately parallel to the surface it contacts, and the barrel muzzle will b'e located sufficiently far from 'the' left' face of shield 24 in Fig. l5 to allow for the depression in workpiece 25. 'I'he variation from perpendicular' and parallel must be within the maximum tilt angie in each case. Of course, the maximum tilt angle (corresponding to the previously mentionedV 12 tilt) will be determined by the contacting engagement location between shieldy 24 and workpiece 25 as well as the length of extension of stop-rod 95; changing the extended length of rod 95 permits selection of this maximum tilt angle within n'xedf limitsf vAlthough the barrel extension 84 in Fig. l5 is only illustrated as Being' used when driving fasteners into a depression on theA workpiece, it should be clearly understood that this barrel extension along with the angle lire control and with the tilt and ready-to-re position indicator 34a maybe used even with a workpiece having a flat surface, such as shown by workpiece 25 in Fig. 2. Then, spring 26 urges flash shield 24 over the barrel extension intoflush relationship with cap 75, as shown in Fig. l, when the tool is removed from the workpiece. The adius'ta'bility of the extension rod 95 permits the rod to be extended so that the barrel muzzle and hash shield 24 m'ustbe substantially flush (with flash shield 24gte1escoped over extension 84) when they contact the workpiece before the tool can be fired. In other words, the extension rod 9'5 is extended from outer tube 54 and bracket 77 a distance equal to the length of the extension barrel 84 in this situation;

The barrel extension- 34 may also be used with a fiat workpiece 25 when an extra long fastener is being driven so that portholes 22d are sure to be uncovered for gas release. The barrel extension adds a substantial distance between the barrel muzzle and the porthole nearest thereto.

When the workpiece 25 is located at any given height from the hoor, the possibility of using the tool either with or without' a' barrel extension' 84 permits making the tool 16 of convenient length. Then, the operator can conveniently grasp hand grip 20v and use thetoo-l without assuming an awkward or uncomfortable position.

The' operational sequence in firing a tooli should now be quite clear. Grasp the sleevegrip 99 in Fig. 1= inone hand withf one finger pressing the release button 97 and grasp the handy grip 20V in the other hand. Locate the t'ool accurately on the workpiece bythe reference marks near the periphery of theflash shield 24 in Fig. 1-2- and thendepress the tool firmly and' squarely against the workpiece. Check the firing pinY indicator 34a tobesure thatr its tip isgenerally flush with the housing so that the toolis in the ready-to-iire position without excessive tilt from the normal to the workpiece surface. Now pull trigger 46: to fire the tool. After firing, continue to depress the safety release button 97 as the tool is withdrawn from the workpiece so that the safety will be automatically operative on release of said button.

Figs. 1-6 andl 117- illustrate a modified form of bayonet or connecting meanslbetween the barrel' assembly andthe breech assembly and more especially between the housings 27k and` 5t1 th ereof.V l'n Figs. 1 and 8 ofthe previously described construction, apair of overlatching pins 63, 63 aread'rnitted' into a` locking groove 51b by a pair of clearance flats 51a. In'- Figs. 16 and 17, four circumferentially spaced inwardly or radially extending lugs 63 are formed integrally with a modified firing mechanism housing 30 in place of the overlatching pins 63 of Fig. l?. Fl'l'hese lugs 63 in Figs. 16: and l`7, all lying in a single plane transverse -toV the barrel4 axis bore, are held when the tool assemblies are locked axially behind correspondingly eircumferentially spaced lugs 5117 extending outwardly from and formed integral with a modied'outer tubecollar 51'. This locked position isillustrated in. Figs. 16 and 1'7. Adequate arcuate spacing is provided between eachf pair of adjacent lugs so that they Vcan slip past each other after the one-eighth rotation unlocking turn has been made to move them from axial alignment of locked position to 45 arcuate spacing of unlocked position. This arcuate clearance spacing tin Fig. 17 corresponds with the hat 51a in Fig. 8 for permitting the removalv of overlatching pin 63. It should be noted that the lug segments 51b.' and 63 in Fig. 17 generally correspond in angular arcuate extent and in axial alignment with the thread segments 221 and 371 ofV Fig. 5 on the barrel 22 and breech lock 37. The interlock pin 66 in Figs. 6, 7 and 8 slides into the cutout formed by the spacing between the axially aligned lugs 51h and 63 of Figs. 16 and 17v in their locked positions when the barrel is in its ready-to-fire position, in the fully locked tool position of Fig. 17. The other parts operate in basically theV same manner as before.

Figs. 18 and' 19 illustrate a modified thread form on the surface of extension rod pictured in Fig. l. The modified thread form on modified extension rod in Fig. 18` is of the buttress form thread with a vertical face at the right with a modified release button 97 having threadsy of a corresponding mating 4type on its segment 97a in Fig. 19 making about a 20 contact on the rod thread periphery `while the remainder of the button bore isrelieved for clearance. The pressure of the rod spring Y94 in Fig. l is balanced against the release button spring 98 so that the rod spring 94 is capable of continually driving the extension rod 95 toward the left since the left face of each thread in Fig. 18, slanted upwardly toward thelri-ght, permitting overriding of the mating threads on the rodk 95 and button 97 until the 4left end of the extension rod' 95 engages the back of the flash shield. Hence, the safety rod is always extended in its safety operative position without requiring the operator to always depress the release button 97'. However, when 'the hash shield 24 and barrel muzzle are pressed against the workpiece to move the tool -to -the ready-to-fire position in Fig. 2, the extension rod 95 will not automatically move toward the right in Fig. 18 since this movement is faces of the rextension rod threads vlvvithithe corresponding thread faces on thethreaded segment 97a'.v Hence, the release button 97 must be udepressed in order to move the tool to the ready-to-re or iring'positio'n.

Although the many `features rof this tool have been described with reference to. only a cooking of the ktiring pin occurring when vthe tool is moved to the Fig. 2 position-so that the tiring pin 1is in the ready-to-iire position, it should Abe readily understood that .many of the vfeatures of vvthis tool could also be used if the' housing movement relativeto the barrel causes automatically not only 'the cooking but also'the release of the'ii'ring pin to explode the charge in the cartridge case y23a as soon 'asrthe 'tool reaches the Fig. 2 position. Then, the Fig. 2 position 'would properly be termed the tiring position. Although "this mode of operation is generally not as desirableias the mode of `operation described heretofore because'it is notas safe, it should be clearly 'understood' that "the inventive concepts that have been described Withreference to the present tool could lalso b e used in a tool not having the re'ady-to-r position.

Various changes in details and arrangements'ofparts can be -made by one skilled 'in the vart without departing fromfthe spirit "of this invention or the' scope of the appendedclaims. l

Whatwe claim is: v f

1f. In a powder actuated tiring device, a housing with Va bore'extending inwardly` from its front, a breechV block in said bore and secured to a barrel, means mounting said .breechY block and housing' permitting relative axial movement'therebetween in said'rbore, a firing pin in said housing behind said 'breech block Aand resiliently biased to move toward said breech block in the sameV general direction and to align with a ring pin hole in said breech block, said ring pin having ardepressible p'awl in the direction opposite to ring pin cooking travel for cocking said ringpin in response to said relative movement 'between said housing and breech block effective to locate'said breech block in said ready-to-re position, means interconnecting said i-ringpin 4with said pawl in such manner as to prevent rotation of said pawl relative to said housing and thereby effective to retain said pavnl lin alignment with said rod.

3. In a powder actuated tiring device, a housing with a boreextending .inwardly from its front, a breech block in said bore secured to a barrel, means mounting said breech block and housing permitting relative axial movement therebetween in said bore but preventing relative ro- -tational movement, a firing pin in ysaid housing behind 'said breech block and resilientily biased to move toward ^said breech rblock in the same general axialdirection and `to align with a tiring pin hole in said breech block, said tirrin'gpin having a resiliently biased depressable lpawifmovable in a direction angularly disposed with the direction of -l'ring pin movement, said breech block being normally disposed inV a rst safety position Within vsaid bore, with `the muzzle end of the barrel extendingforwardly from lthe front of said housing, said 'housing and breechblock being relatively vmovable to locate said breech blocka 'second readysto-re position within said bore with said muzzle end of `the barrel disposed adjacent thefront of said housing, a movable tiring trigger on'sa-id housing and ,operative to release said firing pin only when said breech block is in said second position', rod means on said breech block lfor exerting' a force against said pawl vin the direction opposite to firing pin cooking travel for cocking said firing-pin in response `to said relative movemovableiina direction angularly disposed with the'dire'ci tio-,nmif firingv pin movement, said breech block being 'normally disposed in a first safety position within `said bore with the muzzle endV of the barrel extending forwardly from the front Vof said housing saidhousin'g -and breech. block being yrelatively movableto locate said breech block in a second ready-to-reposition `withinV said bore with said muzzle end of the barrel disposed vadjacent the front of said housing, a movable'iring trigger on 4said housingV and operative Vto release said ring p'in only when said breech block is insaid readyto-reposition and means on'said breech block forfexert- 'lng a force against said pawl'in the direction'vopposite to 4tiring pin cocl'iing travel for cock-ing said-tiring pin in response to said relative movement between said @housing Y and breech block effective h n a to locate said breech block msardready-to-re position. Y

2. In apowder actuated tiring device-ahousingfwith arbore extending'inwardly vfrom-its front, a breechb-lockf' insald bore, securedto a barrel, means mounting-said breech block and housing permitting relative axial'movekmenttherebetween in said bore *but preventing relative rotationalmovementja tiring pin in said `housing i Vbehind said breech block and resiliently biased jto move toward said breech-.block inthe samegeneralaxialdirec- 1 vtion and Ito alignv with ak tiring pin hole lin-said ,breech block, said ningen navingaldepressiblepawi movable f lin a direction angularlyl disposed with the idirectionvof firing pin movement, said breech block `being vrnormally disposed in a rst safety position within said bore, with i f the muzzle end vof the barrel extending forwardly from the front of said housing, said housing and breech block being relatively movable to locate `said breech-block Vin a second ready-to-ire position within said bore with said muzzle end ofthe barrel disposed `adjacent the front of said housing, a movable firing trigger on said housing and operative to release saidV tiring pin only when said breech block is in said second position, rod means on said breech block for exertingA a force against said `pawl ment between 'said housing and breech block VVe'iiec'tive to locate said breech block in said ready-to-re position, lmeans interconnecting the firing pin and pawl for prevent- -ing rotation ofsaid pawl relative to said housing effective to retain *said .pawl inV alignment with said rod, and resilient means extending between'the back of said breech block and Vhousing and normally biasing said breech vblock 'toward said lfirst safety position. y

4. A powder charge actuated tool comprising a'housing; a powder charge -iin'ng means, a barrel for'receving a powder charge, means mounting said barrel and said housing for'endwise relative movement betweena 'normal first safety vposition with the muzzle end of said barrel ex- Htending forwardly lfrom lthe front end Aof said housing 'and a second `ready-to-fire or ring position 'with the Ymuzzle Aend of said barrel disposed adjacent Vthe front end -of said housing, resilient Vmeans'biasing the barrel and the fhousingftoward said 'rst position, andbarrelfengageable latching 'means carried in said -housing and -having latching andy unlatcliing positions with saidbarrel, means normally urging' said latching means toward said latching position' withfsaid barrelY for'preventing relative' l( ymovement` of said lbarrel and housing fully'to sai'd second f f "firing means'for endwise relativefmovement Vbetween a -rst --safety l position V,and j a second 'readyto-iir'e position, resilient meansbiasing'the barrel and said Vtiringv means toward said iiistv position, barrel -engageable latching means havinglatching and 'unlatching positions, :means Vnormally urging said latching'means toward'saidllatchling Vposition with said barrelfor preventing relative move-V ment'ofsaid barrel and iiring'me'ans Vfully to saidyready- -toire`positin, lock means mounted "onthe barrel and biasing action to move into said locking position with said latching means effective to hold said latching means `in said unlatching position, whereby said resilient means jmust be used before said tool can be fired.

6. A fastener driving powder charge actuated tool comprising a powder charge ring means,A a barrel for receiving a powder charge, housing means mounting said barrel and said firing means for endwise relative movement'between a first safety position with the muzzle end of said barrel extending forwardly from the front end of said housing, and a second ready-to-re or ring position with the muzzle end of the barrel disposed adjacent the front of said housing, a flash shield telescopically mounted over said barrel and located near the barrel muzzle, resilient means biasing the barrel and the ring means toward said first position and normally urging the flash shield toward the barrel muzzle for Vengagement with a workpiece into which said fastener is driven, and Vbarrel engageable latching means having latchingand unlatching positions, means normally urging said latching means toward said latching position with said barrel for preventing relative movement of said barrel and ring Vmeans fully to said second position, lock means carried -in said housing and selectively movable intoV locked and unlocked positions with said latching means,'and said lock means being engageable with said resilient means and responsive to its biasing action to move into locking position with said latching means eective to hold said latching means in said unlatching position, whereby said resilient means and safety shield provided for safety must `be present in said tool before said tool can be fired.

7. A powder charge actuated tool comprising a powder charge firing means, a barrel for receiving apowder Icharge, housing means mounting Ysaid barrel and said firing means for endwise relative movement` between a normal first safety position with the muzzle end of said barrel extending forwardly from Athe front end of said housing, and a second ready-to-iire or iiring position with :said muzzle end of the barrel located adjacent the front end of said housing, resilient helical spring means telescoped over said barrel, a stop means on said barrel and 'engageable with one end of said spring means, Ya stop 'ring operatively connected with said housing means and engageable with the other end of said springmean's, said stop ring telescoping over the barrel during said relative movement between said barrel and said firing means,

Ysaid spring means being Veffective through said means engageable with its ends tobias said barrelV and tiring means toward said first position, and barrel engageable latching means carried in said housing located adjacent said stop ring and havinglatching'fand unlatching positions 'with said barrel, means urging saidlatchingmeans vtoward said latching 'position for preventing relative movement of said barrel and iirin'g means fully tosaid second position, and'said'stop ring being responsive to the biasing action of said spring means to exert a force 'b against said latching means effective to keep said latching means in the unlatching position, wherebyrsaid re- 'silient spring means provided for safety-must be operative to exert said biasing'actionbefore Asaid tool can be tired;

' 8. A fastener driving powder charge actuated tool 4comprising a powder Vcharge firing means, a barrel for -barrel'muzzle, resilient helical spring means telescoped over said barrel, stop means comprising a stop disposed at the muzzle end of said barrel and engageable v with .One end `of said spring means, said flash shield being eri- -fastener is driven, said stopY ring telescoping over the bar- -r`el during said relative movement between said barrel and ring means, and barrel engageable latching means operatively engageable with said stop ring and having latching and unlatching positions with said barrel, means normallyurging said latching means toward said latching position for preventing relative movement of said barrel and tiring means fully to said second position, and said `spring means being effective by its biasingraction to exert a force against said stop ring eifective to hold said latching means in said unlatching position, whereby said resilient spring means provided for safety mustV be operative to exert said biasing action beforeV said tool can be fired.

9. A fastener driving powder charge actuated tool comprising a powder charge firing means, a barrel for receiving a powder charge, housing means mounting said barrel and said tiring means for endwise relative movement between a normal lirst safety position and a second ready-to-fire or firing position,a liash shield telesc'opically mounted over Ysaid barrel and located Vnear the barrel muzzle, resilient helical spring means telescoped over saidl barrel, stop means operatively connected with said barrel and engageable with one end of said spring means, means operatively engageable with the opposite endof said spring means and operatively connected with the housing means, Vsaid spring means being eifective through said means operatively engageable with its. ends to bias said barrel and firing means toward-said first posi- Vtionrand urge said flashV shield toward the barrel muzzle for engagementrwith a workpiece into which a fastener is to be driven, said means operatively engageable with the opposite end of said spring comprising latching means actuatable totlatched and unlatched positions with said barrel,` said latching means including gripper means and means normally urging said gripper means toward said latched position with said barrel, and gripper opening means operatively engageable with said opposite end of said spring means being responsive to said-biasing action of said spring means and axially drivable thereby relative to said barrel to engage said gripper means and hold the latter in said unlatched position.

vl0. A powder charge actuated fastener driving tool fore-driving a fastener into a recessed partY of a workpiece,

Vcomprising housing means, a resiliently biased firing pin carriedin said housing means, a-trigger Von said housing means, a barrel Vin said housing meansv and having a breech for receiving a powder charge, said housing means mounting said barrel and firing pin for. a predetermined magnitude of relative movement between a rst safety position with the barrel breech disposed forwardly of `the firing pinV and a second ready-to-re position wherein said firing pin is disposed closelyradjacent said barrel lbreech and in position to be released by said trigger, means operatively connected with said barrel andsaid housing means being effective to normally bias said barrel "andiring pin toward said rst position, means connected with the breech and responsiveto the relative movement of said barrel, housing means and firing pin Vfrom said first to second positions. to cock said firing pin, a ash shield telescopically movable over said barrel adjacent the barrel muzzle and disposed Vforengagement with the surface of said workpiece` surrounding said recessed part with the barrel and ring pin disposed in said ready-to-ireposition and with said barrel extending into said recessed part and .engaging the surface of -said p art intowhich a fastener is 4to be drivemstop means connected with said housingV and'said ash shield and recess side remote lfrom said bore.

Y 4comprising a `powder charge firing means,Y a barrelhavbeing operable to prevent any greater magnitude of relal ntive irnove'mnt between said barrel, housing means and firing pin from being obtained and hence preventing firing of said tool in the event said 'tool is tilted within saidV recessed part, and said trigger being responsive to placingv said b'arr'el substantially perpendicularly against said surface andto 'the said relative movement between said barrel, said housing means and said firing pin to (said secf ondready-'to-iire position to occupy a tiring' pin 'releas` Y ing position. i i Y e ll. A powder charge actuated fastener driving tool for driving a fastener into a recessed part of a workpiece, as Vis deried in claim l0, and wherein'indicator vmeans are operatively connected with said firing pin and visually indicate exteriorly of said housing the readyfto-ii're positioni'n'g of said tiring pin on relative movement between 'said firing pin and said housing.' i

12. In a tool, comprising a pistol grip handle, a tool 'attachment receiving bore in said handle'with one open end for receiving said attachment when not in use, and

flocking means for detachably locking said attachment in said bore, said lock-ing means comprising a one piece resilientspring latch frictionally secured in a recess in said pistol lg'ripghandle 'extending inwardly from 'said openendfin thesame direction `as said bore, `said latch f' having amid-portion bearing against the bore side of the recess' and "having an attachment retainer portion one end'resilientl'y biased over said open endbut swingable away therefrom and having its other end bent back `upon the mid-portion with a sharpdistal end 'engaged/inthe .13.A powder charge actuated fastener driving't'ool comprising a housing means, a powder chargering means, means operatively connecting said housingand Vfiring Vmeans together, va barrel, means mounting said barrel and said housing means for relative movement between a normal iirst safety position and a second readyro-fire or firing position, and adjustable safety locking means operatively connected to one of said housing means Y and `said barrel and having more than two manually sev lectable positive operative or inoperative positions for respectively preventing or permitting travel to the readytodire or -iiring position.

*14. `A powder charge actuated fastener `driving tool 1 comprising "a powder charge tiring means, a barrel means,

meas.`mounting said barrel and ysaid firing means for relative movement between la normal rst safetyriposition land a second ready-to-lire position with said barrel and tiring means in said respective positions 'spaced apart andwadjacerityeach, other, means for moving'said-iring v means to a4 ready-to-re position responsive 'to moveaguas-sas driven, said firing means including manually operable trigger means operatively eonnecte'd'with saidv housing means, means connected with theb'reech and respon'- sive to the relative movement of said barrel 'and tiring means to ksa`id`second positionto cause'said firing means to assume a cocked position, said trigger means occupy'- ing a firing means releasingposition lin said second .position of said tiring 'means and said barrel, and safety locking' means operatively lconnected with `said housing means and selectively actuatable into engagement with said Hash shield toy prevent the relative movement of said tiring means and said barrel to said second position.

16.',A powder chargev actuated fastener drivingtool comprising a housing member, aY powdery charge ,iiring means in said housing member, a` barrel having a 'breech for receiving said vpowder charge, means mounting said barrel and said housing member for relative endwise movement between `a normal iirst safety position 'and'.a second ready-to-iire` or firing positionV with `said lhousing member moved endwise toward the barrel breechin traveling from said rirst to' said second positions, said firing means being -moved endwise betweenV said fir-'st and.

second positions by pressing the barrel muzzlela'gainst the work piece in which saidfastener is to :be driven, a flash shield member telescopically `connected vron said barrel for engaging said work piece, and resilient 'means' normaly biasing said-` barrel and said housingmember l and ring means toward said rst position, safety 'lock'- ing means operatively connected to one of said membersV operative position yas the-shield member and barrel muzzle 17-.QA powder; charge actuated are pressed against the work pieceV so that'movement to v said second position cannotroccur. l

fastener -drivingtool comprising a powder charge firing means including nient 'fromrsaid rstto said second positions, said tiring means including manual .operable ring means for .firing #said lpowder only when the `toolis 1in the re'ady-to-rey position, and adjustable safety locking vmeans"operatively connected to Vone of said lirst two mentioned means and -having more than two manually selectable operativeor inoperative positions yforrespectively "preventnig'br pri mitting travel to the readyetoare position. n v- '.l-5'. A powder charge actuated'fastener driving'tool ing -a breech for receiving a powder charge, housing 4means mounting said barrelv and said tiring means for -ba-rrel breech, Vresilient means normally biasing f said barrel and said tiring 'means toward said rs-t position, -a fla-sh .shield telescopically mounted vover said barrel y zfor, engaging a workpiece into which a fastenerf is to'be V second positions, said tiring means being moved endwise* member, albarrel having a breech for receiving said powder charge, vhousing means mounting said barrel and said firing means -for endwise relative movement between a normal first safety position and a second 'ready-toA-iire position with fsaid tiring means moved 4endwise toward the barrel breechA in traveling from said :first to said second spaced apart positions, said firing means being moved endwise between said iirst 'and second positions by pressing the barrel muzzle against the' work piece fin which said fastenerV is to be driven, a flash shield memberA telescopically connected on said barrel for engaging said work piece, -means on said barrel forpreventing said flash shield from traveling away from said breech vbeyond alixed position with respect to said barrel muzzle,

ymeans for moving said'tiringmeans to a lreadyfto-fire position responsive-tovmovement from said first to said second positions,V` said liring means including 'nrianu'ally`r operable ktiring meansfor lfiring said powder only linthe f-ready-to-re position, and safety locking" means opera-v tively connected `to one of said members and having manually selectable'operative or inoperative positions for respectively preventing or permitting travell to 'the readyto-iire position by stopping the movement in said operative position as the shield member andbarrrelmuzzle Iare pressed Aagainst lthe work piece so thatmovement to said ready-to-firezposition cannot occur.l ,4 Y

18. A powder chargel actuated fastener driving"v tool comprising a housing memben'a powder charge-ring means, a barrel having a breech for receiving said powder charge, rmeans mounting said barrel and said housing Y member for endwise relative movement between anormal first safety position and a second ready-to-re or firing posltion with said firing means moved endwisetoward the barrelbreech in traveling from said lirstgto said between said iirs't and second positions by `pressingrthe barrel'milzzle against the work piece in which ksaid` fasy 'tener 1s tto -be driven, a ilash shield member telescopia 23 cally connected on said barrel for lengagingsaidV work piece, means on said barrel for preventing said ash shield from traveling away from said breech beyond a fixed position with respect to said barrel muzzle, and safety locking means operatively connected to one of said members and having manually selectable operative or inoperative positions for respectively preventing or permitting travel to the second position by stopping the movement in said operative position as the shield member and barrel muzzle are pressed against the workpiece so that movement to said second position cannot occur.

19. A powder charge actuated fastener drving tool comprising a powder charge ring means including a member, a barrel having a breech for receiving V'said powder charge, housing means mounting said barrel and said firing means for endwise relative movement between a normal iirst safety position and a second ready-to-ire or tiring position with said tiring means moved endwise toward the barrel breech in traveling from said iirst to said second positions spaced apart and adjacent each other,VA said tiring means being moved endwise between said first and second positions by pressing the barrel muzzle against the work piece in which said fastener is to be driven, a'iiash shield member telescopically connected Von said barrel for engaging said work piece, and adjustablestop means operatively-connected to one of said members and having manually selectable positions so that when in any predetermined position corresponding with the distance between barrel muzzle and ash shield work piece engagements, the Vbarrel and iiash shield will be against the work piece'when the tool is in said second position.

20. A powder charge` actuated fastener driving tool comprising a housing member, a powder charge ring means, a `barrel having-a breech for receiving said powder charge, means mounting said barrel'and tiring means for endwise relative movement betweena normal iirst safety position and a second ready-to-re or firing position with said tiring means moved endwise toward the barrel breech in traveling from said first to said second positions, said tiringV means being moved endwise between said Jfirst and `second positions by pressing the barrel muzzle against the work piece in which said fastener is to be driven, a flash shield member telescopically connected on said barrel for engaging said work piece, resilientmeans normally biasing Ysaid barrel toward said rst position, and adjustable stop means operatively connected to one of said members and having manually selectable positions so that when in any predetermined position corresponding with the distance between barrel muzzlev and ash shield member work pieceV engagements, -the barrel and Hash shield-member will'be against the Work pieceV when the tool is in Vsaid second position, said shield member and barrel muzzle and the position of said stop means being so located that when the shield member and the stop means are engaged and when the shield'member and muzzle are pressed yagainst therwork piece, the bore of said barrel must be approximately perpendicular to thework piece to move the tool into the ready-to-fire position.

' 21. A powdercharge actuated tool comprising a powder charge `tiring means, a barrel for receiving a powder charge in its breech, means mounting said barrel and Y' 'said iring means for relative movement between a normal 'r-stvsafety position and a second ready-to-fire or firing positionV with said barrel and tiring means in Vsaid respective positions spaced apart and adjacent each other, a breech block covering said breech and detachably connected to said barrel by screw threads with an axis eX- tending in lthe samergeneral direction as the barrel bore, and breech,V loci;V means forrlocking Vsaid breech block against detachment rom'said barrel during tiring said powderV charge comprising a lock pin operatively en- '.gageable with said breech block and barrel and mov- 24 able inthe direction of the barrel axis for locking said breech block by blocking the unscrewing of said threads.

22. A powder charge actuated tool comprising a powder charge tiring means, a barrel for receiving a powder charge in itsbreech, housing means mounting said barrel and said ring means for endwise relative movement between a normal iirst safety position and a second readyto-flre or tiring position with said barrel and tiring meansv in said respective positions spaced apart and adjacent each other, saidvbarrel and said .firing means being biased toward said rst position so that force must be applied to move to the second position, a breech block covering said breechand detachably connected to said barrel, and breech lock means responsive to movement approaching said second position for locking said breech block against detachment from said barrel during ring said powder charge and responsive to movement away from said second position for unlocking, said breech lock means comprising a lock pin and a lost motion connection between said barrel and lock pin for permitting movement of said barrel from ready-to-iire position to said safety position. 23. A powder'charge actuated tool comprising a housing, a powder charge firing means, a barrel telescopically mounted in said housing for receiving said powder charge in its breech, said barrel and said ring means being mounted in said housing for endwise relative movement between a nor-mal rst safety position and a second ready-to-iire or tiring position, said barreland said ring means being biased toward said irst position, said barrel having an elongated slot and cooperating guide means on said housing for guiding in endwise movement between said positions, said slot having a Vwidened porbeing mounted in said housing for endwise relative movement between a normal iirst safety position and a second ready-to-iire position with said barrel and ring means in said respective positions spaced apart and adjacent eachother, said barrel and said tiring means being biased toward said iirst position, said barrel having an elongated slot and cooperating guide means on said housing for guiding in endwise movement between said positions, said slot having a widened portion for cooperation-with said guide means when the barrel is in said ready-to-re position so as to preventV turn jamming the barrel against the side of the slot in the ready-to-iire position so that movement will not occur under said bias toward the iirst position when any force urging it to the second position is removed, :and means for moving said ring means to` a ready-to-ire position responsiveV to movementV from said first to said second positions, said tiring means including manual operable ring means for ring saidV powder when'the'tool is in Vtheready-to-iire position.

25. A powder charge actuated tool comprising a barrel housing, a powder charge iiring means,ia barrel telescopically mounted in said housing with said barrel receiving said powder charge in its breech, means mounting said barrel and Vsaid housing for endwise relative movement between `a normal iirst safety position and a second ready-to-re positionrsaid barrel and said housing being biased toward said iirst position, a breech closure member covering said breech and means for detachably connecting it thereto, said'barrel'having an elongated slot therein, an extension rod -tube positioned under said housing and supported Aatrthe muzzleend `of said l25 housing by a tube end receiving braeke't thereon, a'hinge means connecting said housing and breech closure member, a second tube end receiving bracket means for the Vtube end adjacent said hinge means, and a single screw connecting together the-housing end of saidhinge means,

said second tube end receiving bracket means, and the housing with the' end of said screw projecting into the "elongated barrel slot. j Y

26. A powder-charge actuated tool comprising -a barrel housinga powder' charge tiring means, a Vbarrel telescopically mounted in'said housing for receiving said powder char-ge in its breech, said barrel and said nring means vbeing mounted in -said'housing for endwise relat'ive'frnovement between a normal first safety position and a second ready-to-'iire or -iring position with said barrel andring means in said respective positions spaced 'apart andadja'centfeach other, said barrel-and said firing meansbeing biased toward said first position, a breech block covering said breech and detachablygconnected 'tosaid barrelby screw'threads, said barrel having an elfllgtited'Slot and cooperating guide means on said hous- 'ing jto -prevent unscrewing said vbarrel from ,saidl breech ybleek and to'guide said barrel during endwise movement Veen Vsaid positions, saidslot having a widened porno Vfor cooperation with said guide means during apvch ltofaild in vsaid :second position sofas Ito prevent jtnrnjam'ming the barrel in the second position so that :movement will occur'under said bias towardthe ttirst position when `any force urging it to the second 'position Y isrernoved, and breech lock means von said housing revs'p'c'nsiv'e#to movement approachingisaid second position fo'r locking ispai'dbreech block'against detachment from gsaid` ymeans'being effective when said guide means reaches 3,5

A'ber having a charn'l'erY in its breech, a breech assemblyinbarrel during `tiring said powder, said vbreech lock fthj'ewidest'part of said elongated slot.

Apowder charge actuated tool comprising a powder charge liiring means, a barrel having a breechfor 'rceiving'a powder charge therein, housing'means mount-V `ingsfaid "barrel and said firing means for endwise rela- 'tivemoveinentfbetwee'n "aAiir's-t safety Vposition with "the barrel breech disposed forwardly of thering means, and a second ready-,to-re or tiring positionwith said Iiing Vmeans idispose'd `closely adjacent said barrel breech, a breech block in said'housing means covering said breech and detachably connected to said barrel byscrew threads, l"ai-idffineansinterconnecting said vhousing means, breech block andbarrel'for releasably locking said breech block tol'said barrel during tiring `said powder charge when the Vbreech block and barrelareV fully screwed together, Yand virst Asafetyposition and ajsec'ond readyito-iire Yortiring 'position-with :said barrel and tiring means in jsaidrespective r9 tlensjsracedvrat "asdadiecent eachother, a bree'ch lock Ytele's'copicfin .but non=rotatable relative to itliese'cond'portion of said housing, said breech block coveringfsaid breech and-'detachably connected to said Y barrel byf'screw threads, interlock-means on said housing respon- 'siveftofmovement approaching said second positionfor v looking "said 'breech block againstfdetachment'frm said barre-1 tiring Vsaid powder, 'said breech- .lock means comp'risingan interlock pin carriedby one of said hous- *ingport'i'ons movable inthe direction of the barrel axis ffori'locliing said 'breech block by entering acutout-A in the second lofl said housing portions whenfully screwed to- 'gether '-'for blocking `fthe unscrewing of said vthreads, and bompris'ing movement transmitting means between r-`said 'barrel and pin, the second of said housing portions 'having a shoulder adjacent said cutout blocking thetavel of said pin if said barrel and breech vblock are not `fully screwed together Yso that Ythe v'barrel cannot ybe moved @to the second position. Y 259. A tooLas set forth in claim 28, wherein said housing portions have bayonet means for connectingsaid portions simultaneously with said screw threads, said bayonet means on each housing portion including a plurality 'of radially directed and arcuately spaced radially extending lugs, said interlock pin slidable into the cutout between the'arcuate spacing of adjacent lugs on both housing portions.

` 370. A tool, asset forth in claim 28, wherein said housing portions have bayonet means for connecting'said portions simultaneously .with screw threads, said bayonet' y'means including 'anoverlatching pin carried by, one or" said housing portions ucooperab'le with a .clearancey at leading to a lockingvgroove on the other of said housing portions.

3l. lA powder actuated tool, comprising abarrel vasjs'embly including afbarrel memberhaving'a chamberin its breech, a breech assembly including an interconnected breech block and 'firing means, said'breech block having Y `a telescopic connection with said barrel member breech member and-said breech `block member, said hinge per-l -mittmg a pivotal movement of said breech assembly rela'- and having/a screwthread connection therebetweemand connecting` means between .said barrel assembly and breech assembly comprising a pivot hinge having an elon- ,gated'slot for the telescopic 'action and comprising a ro- -tatableconnectionbetween one-half of said hinge and one ofsid assemblies for the screw action, said assemblies being eitherscrewed together for bring or pivoted open vfor loading.

32. Apowder actuated tool, comprising a barrel mem- .cluding an interconnected breech block,and a ulllpistol ,grip extending-outwardly from the bore axis of said barrel member, said lbreech block vhaving a telescopic connecltion'vvith said barrel member breech `and having a screw thread connection therebetween, connecting means be- ,tween said barrelpmember and breech assembly for'pivtool will remain upright when said members areY eitherV Ysci 'evved together for ring or pivoted open for loading.

33. A powder actuated tool, comprising a barrel mem-Y v berhaving a Abreech formed with a chamber, a barrel jcollar connected with said barrel Vmember Vadjacent said breech, a detachable breech plug insertable into said chamber, Vsaid rkplugf'having a bore therethrough Vfor irecerving- Va cartridge case -for `driving `aV fastener through said barrel member, a 'breech `assembly including `a breech block memberf detachably -interconnected to said barrel member -and a fullxpistcl grip-extending outwardly from the bore axis of said plug, a hingepivotally interconnect- .ing s aid barre-l collar and said breech assembly and having connecting ymeans Yto permit a relative telescopic i movement of said barrel member and said Ybreech'block member, Ya 'screw thread connection between said Ibarrel tive to Asaid barrel member, said connecting means on saidhinge `also permitting a relative rotatable movement between Asaid barrel member and said 'breech block meniber, said breech assembly and said barrel member being selectively disposed between a cartridge case yloading position and 'adtool assembled and loaded position in response ,to ysaid. relative pivotal, telescopicand rotatable movep 1ments, a deector pad shield mounted on the muzzleend .Y

l 27 of said barrel member for engagement with a surface into which a fastener is to lbe driven, said shield having its peripheral edge disposed for engagement with said surface at a predetermined lateral distance `from the barrel member axis, and said hinge and connecting means when the tool is disposed in Ia vertical upright position and the barrel member and said breech assembly are disposed in said cartridge case loading position, thus locating the resultant center of gravity of said barrel member and breech assembly within the boundary of the peripheral edge of .said deflector pad shield,

34. An explosive tool comprising a barrel, a firing pin, a housing assembly including a mounting for said firing pin, means mounting said housing assembly for manual axial movement relative to said barrel, means normally biasing the firing pin toward the breech end of the barrel, means connecting said barrel and said housing assembly including la pivot pin transversely of the longitudinal axis of the barrel for pivoting said housing assembly for movement away from said ybarrel for loading said barrel with a fastener unit `and toward -said barrel to a closed ring position, means on said barrel and said housing assembly for interlocking said barrel and said housing assembly in ring position, means Ifor supporting a breech block in said housing assembly,rmeans carried by said breech block for engaging and cocking said tiring pin against its resilient bias as said housing assembly is manually moved axially of said barrel, and means includinga pivoted member carried by said housing for releasing said firing pin.

35. A fastener driving powder charge actuated tool comprising a powder charge tiring means, a barrel for receiving Aa powder charge, housing means mounting said barrel and said firing means for endwise relative movement between a normal iirst safety position and a second ready-to-re or tiring position, a flash shield telescopically mounted over said barrel and located near the barrel muzzle, said flash shield having tube means disposed radially outwardly of said barrel and defining an annular cavity therebetween, said cavity being closed at its forward end adjacent said barrel muzzle, resilient helical spring means telescoped over said barrel, stop means comprising a stop disposed at the muzzle end of said barrel and engageable with one end of said spring means, said flash shield being engageable with said stop, a stop ring operatively connected with said housing means and engageable with the other end of said spring means, said spring means being effective through said stop means and stop ring enga-ging its ends to bias said barrel and firing means toward said first position and ur-ge said flash shield toward the barrel muzzle for engagement With'a workpiece into which a fastener driven, said stop (ring telescoping over the barrel during said relative movement between lsaid barrel and firing means, barrel engageable latching means operatively -engageable with said stop ring and having latching and unlatching positions with said barrel, means normally urging said latching means toward said latching position =for preventing relative movement of said `barrel 1and ring means fully to Vsaid second position, said spring means being effective -by its biasing Iaction to exert a force against said stop ring effective to hold said latching means in said unlatching position, whereby said resilient spring means provided for safety must be operative to exertsaid biasing action before said tool can be fired, and port means formed in .said barrel and communicating with said annular cavity, said port means being operable upon the tiring of said powder charge to vent the explosive gases thereofY into .fastener driving bore with means for receiving and firing "28 mounting saidbarrel for relative endwise movement of said housing means includingra front housing tube spaced radially from said barrel and open at its front end, a

-flash shield extending laterally and engageable at least peripherally with said workpiece surface outwardly about said barrel, means for mounting said shieldV opposite said open end over said barrel near the'muzzel for relative telescoping movement with respect to said barrel, said barrel having a plurality of longitudinally and annularly distributed gas exhaust ports intermediate its ends and disposed nearer said muzzle, said shield mounting means including tube means extending rearwardly from said shield into said open end and disposed inwardly of said housing tube in telescoping relationship therewith and radially outwardly of said barrel to define an annular blast chute outwardly of said tube means and open at the front end and a gas release chamber surrounding the barrel in communication with said ports, said chamber having a front end oriced for passing the barrel and being substantially closed at its front end adjacent said muzzle and shield and open at its rear end in communication with Vsaid blast chute, means for biasing said shield forwardly toward said muzzle, a laterally Vextending stop disposed forwardly of said shield and vmounted on said muzzle for coacting with said shield and tube means so as to constrain said biased shield against unlimited forward movement ahead of said muzzle and to constrain said tube means and the included forwardly closed chamber into disposition at all time opposite said ports even when said housing and its tube is at the limit of said endwise movement rearwardly of said barrel, whereby upon tiring of said charge and substantial driving of said fastener at said muzzle into said workpiece surface, the residual gases in said bore rearwardly of said fastener are evacuated from said bore Ythrough said ports into `said chamber and from its op'en end into said blast chute to create components of forces acting upon the closed end of said chamberA and the `shield opposite said open end of said chute to thrust both said shield and muzzle into increased pressure engagement with said workpiece surface in counteraction against the opposing force of recoil encountered.

37. The tool of claim 36 including a barrel extension having means at the rear end thereof making said extension detachably mountable on the muzzle of the barrel upon removal of the stop means therefrom and having when so mounted a fastener driving bore aligned with the barrel bore for increasing the eifective length of the barrel for extending operatively into a deeply recessed portion of the workpiece surface, means at the front end of the extension for detachably remounting said stop there, and wherein the shield mounting tube means is not only in telescoping relationship but also'of sui`u`cieut length, when constrained by said remounted stop, to remain in telescoped overlapping relationship with the open front Aend of the front housing tube, whereby both said annular blast chute and gas release chamber formedrby said tubes constitute a telescopically extendable exhaust chamber about'the barrel adjacent its exhaust ports, said housing tube being endwise movable relative to the eX- tended Vbarrel assembly between a first position with said housing tube spaced farther from saidstop and a second position with said tube-spaced closer to said stop, and Ywherein the shield Vis yengageable` substantially all around the barrel Vaxis with a portion of the workpiece surfacel at any preselected position between said stop andhousingltuba there being mounted on said housing means a tiring means,.means operatively connected to the barrel andrresponsive to movement from said first to said second positions for changing said firing means `from a safety to a read-to-iire condition, and adjustable abutment. means selectively'interposable between said Vhousing tube and shield in correspondence. with theselccted position of said shield for stopping the housing tube by abutment with said shield from further'move- 

